Xref: utzoo comp.databases:7573 comp.object:1982
Path: utzoo!utgpu!news-server.csri.toronto.edu!neat.cs.toronto.edu!vinay
Newsgroups: comp.databases,comp.object
From: vinay@ai.toronto.edu ("Vinay K. Chaudhri")
Subject: Predicate Locks
Message-ID: <90Oct18.180225edt.12896@neat.cs.toronto.edu>
Organization: Department of Computer Science, University of Toronto
Date: 18 Oct 90 22:02:38 GMT
Lines: 32



The idea of using predicate locks for database concurrency control
has been around for over ten years.  But still there are not many
commercial systems which use predicate locking as a primary method
for concurrency control.

One reason for this lack of applicability is because it is not 
computationally inefficient to check overlap between two predicate
locks.  People have given suggestions for developing some heuristics
but there does not seem to be any comprehensive approach available.

Another difficulty seems to be in devising an efficient implementation
technique for predicate lock table.  Maintaining a predicate lock
table of some reasonable size (say 100) and comparing a new predicate
against these 100 expressions is prohibitive, leave aside the 
computational reasons.

My question is the following:  Are there really no commercial systems
that use predicate locking ?  Are the reasons for their in-applicability
as cited above are correct ?  Are predicate locks dead as a research
or application area ?



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Vinay K Chaudhri

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